The present invention relates to converting signals, and more particularly to conversion of bi-directional signals characterized in that the signal includes indicia corresponding to a distance, in time or position, and that a converted signal comprises further indicia corresponding to a non-integral multiple of the indicia.
By way of example, in machine tool and position indication applications, encoders (be they rotational, linear or the like) are used to indicate a position of a work piece or a machine part. It is often necessary, however, to convert the output of the encoders (or position indicators) from their fixed number of indicia per unit (e.g., fixed number of indicia per unit of rotation, fixed number of indicia per unit of length, or otherwise) to a number of indicia per unit that corresponds to some aspect of the work piece or machine tool position.
Industry standard rotary shaft encoders, for example, are manufactured with many different numbers of counts per revolution (in many different resolutions) in an attempt to cover the mechanical and precision needs of machine tool position indication applications. However, the resolutions are limited to integer values, i.e., whole numbers of counts per revolution, leaving one to select only a close match, rather than the precise number of counts per revolution desired, and then to use custom gear trains, or complex processor-based computational conversion systems, in order to obtain a desired number of counts per revolution
For example, to generate a converted output comprising a count, i.e., a pulse, every 0.5000 inches on the perimeter of a 25.000 inch diameter drum, and whose shaft is mechanically coupled to a 1120 count per revolution, i.e., pulse per revolution, rotary shaft encoder, it is necessary to convert the pulse output of the rotary shaft encoder from a whole number of pulses per revolution to a non-integer number of pulses per revolution.
At the same time, however, for machine tool applications, the converted output must be accurate at various, and varying rotational speeds, as well as accommodate reversals in direction as, for example, the drum is rotated forward and backward at various and varying speeds.
The present invention addresses the needs above as well as others.